By Brenda Goodman, CNN
(CNN) — President Donald Trump signed an executive order this week that seeks to dramatically reshape vaccine policy in the United States, including a change that contradicts one of his other stated goals: to give children fewer shots.
Trump’s order says the combination vaccine that protects against measles, mumps and rubella, called MMR, “should be administered in three separate single-disease shots,” and all childhood immunizations should be given at separate medical visits.
Immunologists and vaccine experts say there’s no valid reason to do that. Splitting up and spreading out childhood vaccines would be a seismic shift for families and a complicated, costly pursuit for the country that would only leave more people vulnerable to preventable diseases.
A combination MMR vaccine has been used in the United States for more than 50 years. Scientific studies have consistently shown that combination vaccines like MMR increase vaccination coverage and vaccine confidence, and they do that partly by reducing the total number of shots, which can be scary for kids and their parents.
Merck, which developed the original MMR combination shot, stopped supplying single, or monovalent, vaccines against measles, mumps and rubella in the US in 2008. In a letter to doctors explaining the change, the company said the combined vaccine “is preferred” because it “eliminates the need for 3 separate injections and reduces the chance of delays in helping protect against any of these potentially serious diseases.”
The US Centers for Disease Control and Prevention agrees. “No published scientific evidence shows any benefit in separating the combination MMR vaccine into three individual shots,” the agency says on its website.
Speaking from the Oval Office, Trump and other administration officials listed a litany of reasons for the recommended changes: to emphasize parental authority, to improve trust in vaccines, to align with other countries’ vaccine schedules.
Splitting up shots is “inconvenient … but it’s something that I think will have a huge impact on autism,” Trump said Monday, despite decades of research showing there’s no link between vaccines and autism.
Trump claimed that “large amounts – like vats of vaccine – are currently pumped into your child’s body.” He held up a graphic, created by groups that oppose vaccine mandates, showing a baby surrounded by needles.
At one point, he said that this supposedly large volume of fluid – “the size of a bottle of soda” – was dangerous.
The standard dose of MMR vaccine given to children around 12 months of age is 0.5 milliliters, or CCs, about one-tenth of a teaspoon.
No evidence new shots are needed
There’s just no there there, said Dr. Walter Orenstein, professor emeritus at Emory University and associate director of Emory’s Vaccine Center.
“MMR doesn’t cause autism, and it just would make it much more of a hassle for people to get those vaccines and would likely lead to decreases in coverage, even in people who wanted to get their shots, because they would have to make several more visits to get the vaccines rather than in a single visit,” Orenstein said.
Others put it more bluntly.
“These recommendations are stupid,” said Dr. Stanley Plotkin, a vaccine developer and emeritus professor at the University of Philadelphia.
“They’re unscientific, and they will result in more disease in this country than we’ve had before,” said Plotkin, who is the author of a widely used medical reference on vaccines.
The US vaccine schedule is carefully crafted and is continually studied and refined, said Dr. Angela Rasmussen, a virologist at the Vaccine and Infectious Disease Organization at the University of Saskatchewan in Canada, and the editor of the journal Vaccine.
“This vaccine schedule did not happen overnight,” Rasmussen said.
Before it’s added, every vaccine is given a full evidence review by the CDC’s Advisory Committee on Immunization Practices, which can take months, she said. But even after it’s added, she said, the CDC and the US Food and Drug Administration have multiple systems that are continually monitoring for safety signals.
“And if a safety signal comes up – and sometimes even if not, if it’s a vaccine that’s brand-new or it’s being expanded to a new population – then there will be a work group that basically does this deep dive and looks at that vaccination,” Rasmussen said. “And then if there are any changes, they will make those.”
Although it may seem safer to space out a child’s shots rather than get all the immunizations recommended at a single visit, Rasmussen said, there’s a risk in doing that, too.
“I think they’re playing on very human emotions, and they’re doing so intentionally,” she said. “Most people are going to respond to that type of thing where it’s like, ‘well, better be on the safe side, especially as far as my kid’s health is concerned.’”
Even if parents intend to come back, it’s easy to get busy and just forget.
And spreading out shots is not necessarily safer, because the diseases that vaccines prevent or make milder can have consequences that are much more serious than the fever or muscle soreness that can follow vaccination.
“Your child could die of measles or the flu,” Rasmussen added.
During the last flu season, more than 190 children died of influenza, according to the CDC, and most of them were unvaccinated.
In 2025, there were three deaths confirmed to be linked to measles, all in people who were not vaccinated. Roughly a quarter of children under age 5 diagnosed with measles in the US last year were hospitalized.
Although Trump and his advisers say they want to give parents more choice, Plotkin said, what they’re really doing is making everyone less safe.
“It sounds reasonable to have people make their own decisions, but the point is that their decisions affect everybody else,” he added. “If they don’t vaccinate, the infection is more able to spread and to attack people who are immunosuppressed or can’t respond to vaccines. So the whole idea is ridiculous.”
New vaccines would be complicated and costly
Trump’s executive order gives US Health and Human Services Secretary Robert F. Kennedy Jr. 90 days to present a plan about how to offer childhood vaccines, “starting with MMR,” as single doses.
Currently, there are no individual vaccines for measles, mumps and rubella available in the United States. In an interview with CNN on Tuesday, Kennedy pledged to make individual vaccines available quickly.
“We’re going to do it as quickly as we can,” he said. “We don’t intend to take any vaccines away from people, but I think it makes sense to give people an option.”
But developing and distributing single-antigen vaccines would probably be complicated and costly, according to vaccine makers.
Merck, which makes two of three currently licensed MMR vaccines used in the US, said that there’s no scientific reason to split up the vaccine into its components.
“Splitting the MMR vaccine into three separate vaccines would not be a simple process,” the company said in a statement this week.
Reformulating would require new development and testing.
“It could take years – potentially as many as 10 – to meet the safety and efficacy requirements to obtain FDA approval and then begin manufacturing and commercialization,” Merck noted.
GSK, which makes another combination MMR shot, said it stands by the safety of its vaccines, which have been used for decades.
“These vaccines are clinically proven to provide vital protection against infectious disease, and support public health goals by reducing missed doses, improving immunization coverage, and minimizing the burden on families and healthcare systems,” the company said.
Monovalent vaccines are available in some places. They’re sometimes used by low- and middle-income countries as catch-up vaccinations or to tamp down outbreaks.
The public-private partnership Gavi, which works to increase access to vaccination, has offered monovalent measles vaccines to the countries it works with since 2007 and a combination measles-rubella shot since 2013.
One particularly interesting test case is Japan, one of the rare places where monovalent shots have been in use recently.
A test case in Japan
“Why is it that in Japan, you can get a separate measles shot, a separate mumps shot, a separate rubella shot, but in America, it has to all be packaged together?” Stephen Miller, the White House’s deputy chief of staff for policy, asked at Monday’s Oval Office event.
Japan began using a combination vaccine against measles, mumps and rubella in 1989, but it was short-lived. The vaccine included a mumps strain called Urabe that was linked to an increase in meningitis in about 1 in 900 people who got that country’s original MMR vaccine — a higher rate than expected. (The vaccine used in the US has always used a different mumps strain, called Jeryl Lynn, which is not linked to meningitis.)
Lawsuits followed, and a Japanese court ruled that the Ministry of =Health failed to warn vulnerable people that the vaccine could have contraindications. Vaccine hesitancy in that country surged.
As a result, Japan stopped using its combination MMR vaccine in 1993 and instead made single-component shots available for measles, mumps and rubella.
But after the single-component shots came into use, infections there began to rise.
A 2001 measles outbreak included an estimated 265,000 cases, most in babies. That led to a campaign urging parents to give their children the measles vaccine as a gift for their first birthday, which helped raise vaccine coverage in young kids from 50% up to 90%.
In a further effort to stop outbreaks, Japan moved back to a combined measles-rubella vaccine in 2006. It’s standard for children to get a dose at one year of age and another before they start school, similar to the schedule in the US.
The policy shift to the MR vaccine led to the elimination of regular measles transmission in Japan in 2015. A monovalent measles shot is licensed, but it is not commonly used.
Meanwhile, mumps has continued to be a problem. Mumps vaccination is voluntary and given with a separate standalone vaccine that parents pay for. As a result, mumps vaccination rates are low, and Japan has large outbreaks every three to five years. One of the largest spanned 2000 to 2001, with an estimated 2 million cases, mostly in children.
Most children recover completely from the mumps, but it can also lead to deafness, inflammation of the lining of the spinal cord and brain, and impaired fertility.
In March, a panel that advises Japan’s Minister of Health on vaccinations gave its nod to a new version of the MMR vaccine made by Daiichi Sankyo, which would move the country back to a trivalent vaccine.
There was another finding in Japan’s experience with monovalent MMR vaccines: After the country switched to individual shots, autism rates continued to rise there.
Reviving discredited claims
Trump’s executive order on childhood vaccines does not mention autism, but the president again floated the idea that vaccines may cause somehow cause autism when he signed the executive order and suggested that splitting up vaccines would help.
Hundreds of scientific studies published in peer-reviewed medical journals have investigated the question of whether autism is linked to vaccines. Their overwhelming conclusion is that there’s no connection.
This avalanche of research followed a now-infamous 1998 study published by a British gastroenterologist named Andrew Wakefield in the journal the Lancet. The study connected gut inflammation in 12 children to neurodevelopmental disorders such as autism. Parents who were interviewed for the study claimed that their children’s behavior had regressed after they received the MMR vaccine. After the study’s publication, Wakefield went on to recommend splitting the vaccines into single shots.
Wakefield’s original study was retracted in 2010. He lost his license to practice and moved to Texas, where he became an active supporter of the anti-vaccine movement.
Wakefield, who’s also an ally of Kennedy’s, met with Trump while he was campaigning for his first presidency in 2016 and was invited to the 2017 inaugural ball.
To scientists, the idea that the link between vaccines and autism simply hasn’t been studied enough – as Kennedy often claims – is astounding.
There are at least four different lines of evidence that have failed to find any connection, said Angelica Ronald, professor of psychology and genetics at the University of Surrey in the UK.
First, “Large population studies of millions of children show that autism is not linked to MMR,” Ronald said in a comment to the nonprofit Science Media Centre. Second, “Further evidence comes from studies in countries in which the MMR vaccine was halted such as Japan. In Japan, when the MMR vaccine was stopped, autism cases still continued to rise,” she said.
“Furthermore, genetic factors are the largest known cause of autism and this is supported by many robust, well-powered studies. Finally, some traits related to autism emerge before children receive the MMR vaccine,” Ronald said – the third and fourth lines of evidence.
Autism advocates say they are frustrated by the continued focus on this discredited theory, which detracts from study of the real causes of the disorder.
“No environmental factor has been better studied as a potential cause of autism than vaccines,” Dr. Alycia Halladay, chief science officer of the Autism Science Foundation, said in a statement after the executive order was signed.
“That includes vaccine ingredients as well as the body’s response to the vaccines. All this research has determined that there is no link between autism and vaccines. This is consistent across multiple studies, repeated in different countries around the world, including those mentioned in today’s press conference. Separating vaccines into multiple visits has also never been shown to prevent autism.”
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